A 3.15 10⁶ M standard solution of a coloured complex exhibited an absorbance of 0.386 at 545 nm in a 1.000-cm cuvet. A blank solution made from distilled water had an absorbance of 0.019.

i) Find the molar absorptivity of the coloured complex.

The absorbance of an unknown solution was 0.235.

ii) Find the concentration of the unknown.

would it be this?

or this?

i) Molar absorptivity, = (0.386 - 0.019)/(3.15 106 1.000) = 1.19 10^5 M^-1 cm^-1

ii) Concentration of unknown, C = (0.235 - 0.019)/(1.19 10^5 1.000) = 1.97 107 M

since) A=ClMolaralssorptivity=ClA=3.15106M1.000cm0.386=1.23105M1cm1IfA=0.235So,c=lAc=1.23105M1cm11.000cm0.235C=1.92106M